The present invention relates to a system for reducing the discharge of pollutants from underground gasoline storage tanks. The system is arranged to discharge pollutant free air when the pressure within the system reaches a predetermined level. Air to be discharged is separated from gasoline vapor within the storage system prior to its discharge.
U.S. Pat. No. 5,464,466, to Nanaji et al., describes a fuel storage tank vent filter system where a filter or fractionating membrane is used to capture pollutants from the vapor vented from the system""s fuel storage tanks. A property of the membrane is that it will capture or collect selected pollutants including hydrocarbons. The captured pollutants are drawn from the membrane as a liquid and returned to the fuel storage tanks. The fractionating membrane comprises a plurality of stacked and bound thin sheets. Each sheet has a hole formed in its center to form an aperture in the stack extending axially from end to end. A perforated removal pipe must be positioned in the axial aperture to enable the captured vapors to be drawn out of the membrane under a vacuum created by a vacuum pump. The throughput of the system is limited because pollutant molecules, as opposed to air molecules, must be pulled through the fractionating membrane in liquid form. U.S. Pat. No. 5,571,310 discloses the use of such a membrane in an organic chemical vent filter system. Harmful volatile organic compounds (VOC""s) are drawn through the membrane by using a vacuum pump to create a pressure drop of one atmosphere across the membrane. The pump is positioned between the membrane and the tanks, as opposed to between the membrane and the atmosphere.
These prior art systems are inadequate, however, because, to achieve adequate throughput, a substantial pressure drop, e.g., one atmosphere, must be created across the fractionating membrane. Further, the fractionating membrane of these prior art systems, and the associated hardware, is typically too large and costly for many applications. The pumping and fluid transfer system is likely to be more costly and difficult to assemble because of the relatively high levels of vacuum created in the system. Finally, the prior art systems do not expel substantially pollutant free air to the atmosphere. Rather, pressure within the tanks is reduced by merely condensing the pollutant vapors to liquid and returning them to the tanks. Accordingly, there is a need for a compact fuel storage system vent filter assembly that provides improved filtering and throughput at a competitive cost.
This need is met by the present invention wherein a diagnostic fuel storage system is provided including a pressure sensor configured to monitor pressure at one or more diagnostic points within the system. In accordance with one embodiment of the present invention, a diagnostic fuel storage system is provided comprising at least one storage tank, a filter system, at least one pump, and at least one pressure sensor. The storage tank includes a fuel vapor vent port. The filter system comprises a filter input port coupled to the fuel vapor vent port. The pump is positioned to cause fuel vapor to pass through the filter input port. The storage tank, the filter system, and the pump are arranged such that the storage tank and selected fuel vapor ducts in communication with the storage tank operate below atmospheric pressure. The pressure sensor is configured to monitor pressure at one or more diagnostic points within the storage tank, the selected fuel vapor ducts, and combinations thereof. In this manner, the pressure sensor is operative to provide an indication of operation above atmospheric pressure.
According to another embodiment of the present invention, a diagnostic fuel storage system is provided comprising a plurality of fuel storage systems, a central data processor, and a communications link coupling the central data processor to each of the fuel storage systems. The central data processor is configured to process pressure data sensed by the pressure sensors.
Accordingly, it is an object of the present invention to provide a diagnostic fuel storage system configured to monitor and improve fuel storage system performance. Further, it is an object of the present invention to provide a filter system and associated pumping hardware designed to optimize the efficiency of the fuel storage system. Other objects of the present invention will be apparent in light of the description of the invention embodied herein.